Process and material for the development of diazotype copies



United States Patent 4 Claims. in. 96-49) The present invention relatesto reproduction processes and refers more particularly to a process andmaterial for the development of diazotype copies.

In the diazotype process, the photosensitive copying material containinga diazo compound and a compound capable of coupling with the diazocompound is developed by the action of alkaline-reacting substances.

In an alkaline medium, an azo dye forms in the areas not alfected bylight, thereby making the image visible. Gaseous ammonia is Widely usedas the alkaline developer in practice today. However, it would bedesirable to avoid the use of ammonia or other gaseous substances whichmust always be present in excess to insure thorough development, sincespecial devices are required to prevent escape of gas from thedeveloping equipment.

Liquid alkaline developer solutions have also been used. By using these,the disadvantages of development wtih gas are substantially avoided, butthe resulting copies are obtained in moist form which in many cases isundesirable (for example, when making many copies in ofiices).

Basic-reacting substances which are liberated by heat and which then actas developers have also been coated with the essential diazo chemicals.Thus urea which forms ammonia has been used. Diazo materials contain ingsuch substances have the following disadvantages: relatively poorstorability and stability, and for development, high temperatures andprolonged developing times requiring lengthy warm-up period even ininsulated equipment.

It has now been found that the dry development of diazotype materialshaving excellent shelf life by the brief action of heat to produce good,high contrast copies is possible. The process is characterized byallowing infrared radiation to act briefly on a developer sheetcomprising a support, infrared-absorbing matter, and at least onealkaline-reacting substance in free or combined form. Under the actionof the heat generated by the infrared radiation and the master, thisalkaline-reacting substance which is disposed in surface contact withthe imagewiseexposed diazotype material changes its aggregation to oneof gas, vapor, or liquid. As a result, the alkaline-reacting substanceis transferred to the surface of the diazotype material and creates theproper alkaline environment necessary for development.

Therefore, one object of the present inevntion is to provide a processand material for the dry development of diazotype material, whichovercomes the disadvantages of the prior art.

Another object is to provide a process and material for the quick, drydevelopment of diazotype materials having excellent shelf life.

Other objects Will become apparent in the course of the followingspecification.

The alkaline-reacting substance and the infrared absorbing matter may beon the surface of or inside the support. Suit-able supports are paper,plastic foils, metal foils, and the like.

The paper may contain the infrared-absorbing matter such as carbon blackand the alkaline reacting substance uniformly dispersed infinely-divided form over the whole of the paper. Such a developer sheetmay be obtained 3,318,599 Patented May 9, 1967 ice by impregnation ofcommercial porous paper loaded with carbon black with suitable solutionsof the alkaline-reacting substances. Non-porous paper or papers whosepores are closed by an impermeable coating may contain thealkaline-reacting substances in the form of a thin surface layer.Finally, the papers may have both the alkaline-reacting substance andthe infrared-absorbing matter applied to one or both surfaces of thepaper support.

The same arrangements may exist also when plastic films of polyethylene,polypropylene, cellulose acetate, and the like are used. Thus, both thealkaline-reacting substance and the infrared-absorbing matter may beadded to the plastics during casting, in the melt, or during extrusion,and the resulting developer sheet contains these substances in ahomogeneous distribution. However, this possibility may only \beutilized when the melt or the extrusion temperature of the plastics isbelow that at which the alkaline-reacting substance becomes active asdeveloper with a change in its state of aggregation. The plastic filmsmay contain carbon black homogeneously distributed within the supportand the alkaline-reacting substance on their surface. However, theinfrared-absorbing matter may also be applied together with thealkaline-reacting substance to the plastic support surface whichexpediently faces the diazotype coating.

In the case of metal supports, the infrared-absorbing matter may beapplied to the surface facing the source of radiation, and thealkaline-reacting substance may be applied to the surface facing thediazotype coating. Both substances may also be present together on thesurface in contact with the diazotype material. Liquid alkalinesubstances With which the support may be impregnated transfer themselvesto the diazotype material by distillation. Solid alkaline-reactingsubstances are converted into the molten state and then transferred tothe diazotype material. Moreover, solid alkaline-reacting substances mayalso be vaporized onto the diazotype material by sublimation. Aparticularly advantageous embodiment of the process is one in which thealkaline-reacting substance is initially not in free form but inphysically or chemically combined form, is liberated by the action ofheat, and transfers itself onto the diazotype material as gas, vapor, orin the form of a melt. Coatings which contain the alkaline-reactingsubstance in such combined form are distinguished by a particularly highstability and long shelf life.

Alkaline-reacting substances which may be used in free form arealiphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic amineswhich are sublimable, distillable or fusible at the temperaturesgenerated by the infrared radiation. They may be of primary, secondary,or tertiary nature. Diamines and polyamines may also be used. Thehydrocarbon radicals of the amines may contain functional groups,provided these do not have a deleterious efiect on the production ofphotocopies. Thus, hydroxy alkylamines or alkoxy alkylamines may beused. Aromatic amines may also contain hydroxy, ether, thioether, ester,keto or nitro groups on the nucleus, or fluorine, chlorine, or bromineatoms. Amines or substituted amines which have an injurious effect onthe human system are not used. Nor are amines with very high carbonnumbers generally used because at the preferred temperatures in thepresent process (50 C. to 200 (3.), they are undistillable,unsublimable, or infusible, or only very difiiculty so. Amines with notmore than 30 carbon atoms are therefore generally preferred.

Some of the suitable amines are: alkylamines such as N-dodecylamine,oleylamine, and stearylamine; lower alkanolamines such asmonoethanolamine, diethanolamine, triethanolamine, l-aminopropanol-3,and triisopropanolamine; lower alkylene diamines such as ethylenediamine and 1,6-diaminohexane; araliphatic amines,

amines such as benzylamine; and aromatic amines such as aniline,o-toluidine, rn-toluidine, p-toluidine and alphanaphthylamine.Polyalkylene-polyamines may also be used.

Suitable substances which produce a liquid or volatile alkaline-reactingsubstance are urotropine, urea, thiourea, methylurea, ethylurea,methylthiourea, guanidine, and the ammonium salts of monobasic orpolybasic inorganic or organic acids, especially carboxylic acids.Examples are ammonium carbonate, ammonium formate, ammonium acetate,ammonium succinate, ammonium lactate, ammonium citrate, ammoniumtartrate, ammonium phthalate, and ammonium benzoate. Naturally, ammoniumsalts in which the liberated acid by-product has a deleterious effect onthe production of photocopies are not used. Finally, the ammonia oralkaline-reacting substances may also be used in the form of complex,inclusion, or absorption compounds which liberate the base at thetemperature used.

It is also possible to use mixtures of several alkalinereactingsubstances. Sublimable, distillable, and fusible basic substances may bemixed with substances which do not form a base until they are heatedtogether.

Substances capable of wholly or substantially absorbing infrared raysfor the present invention are varieties of carbon such as carbon black,animal charcoal and graphite.

In order to coat these supports, the alkaline-reacting substances areapplied from aqueous or organic solutions to a support capable ofabsorbing infrared rays. In order to improve the adhesion of thesubstances to the support and to increase the shelf life of thematerial, binding agents may be added to the solution. Such agents maybe polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetate,after-chlorinated polyvinyl chloride, polystyrene, polyamides, orpolyesters. A suitable developing sheet may also be obtained by coatingthe support with a melt or by extrusion of a mixture of thealkaline-reacting substances with waxes or thermoplastics. During thesubsequent developing process, the waxes together with thealkaline-reacting substance transfer themselves to the diazotypematerial. The impregnation of the support is likewise effected with theaid of suitable aqueous or organic solutions of the alkaline-reactingsubstances.

All known infrared radiators may be used as sources of radiation. Thetemperatures which these radiators produce in the absorption coating areexpediently between 50 C. and 200 C. Especially preferred aretemperatures between 100 C. and 150 C. The active period of radiation onthe developer sheet consisting of support, the infrared-absorbingmatter, and the alkaline-reacting substance is several seconds and isgenerally not greater than ten seconds.

The developer sheet is preferably disposed between the diazotypematerial and the source of radiation, but this is not absolutelynecessary. The infrared radiation may :also be directed from the side ofthe diazotype material. This applies to a metal support bearing thealkaline-reacting substance on the surface facing the diazotypematerial.

One expedient embodiment of the process consists in covering the exposeddiazotype material of a specific size with the developer sheet of thesame size, and passing the two-ply assembly at a speed of several metersper minute through the radiation field of an infrared radiator while thediazotype material and the developer sheet are in close contact witheach other. The radiator may be focused.

To avoid the positioning of individual developer sheets on the diazotypematerial to be developed, it is expedient to use the developer sheet asan endless strip over two or more rollers. The developing process thentakes place in the space between two rollers. An ordinary commercialradiator fitted with a contact switch and designed to radiate onlyduring the period necessary for actual development may be used,

The following examples further illustrate the invention and are notintended to limit the scope of the invention.

Example 1 A tissue paper permeated with carbon black at a coating weightof 30 grams per square meter was impregnated with a ten percent aqueoussolution of ammonium carbonate. After drying, one sheet of theimpregnated material was laid on an exposed ordinary commercialphotocopying diazotype paper. The two papers were then passed at a rateof several meters per minute through the focal line of a focusedinfrared radiator with an output of 1,350 watts. Care was taken by meansof rollers to insure good contact between the two papers. The infraredradiation was absorbed by the carbon black to generate heat of about 120C. As a result, the ammonium carbonate decomposed into ammonia andcarbon dioxide. The liberated ammonia permeated to the surface of thephotocopying material where coupling took place in the unexposed areasdue to the alkaline reaction of the ammonia, and the desired visibleimage was obtained.

Example 2 A solution of ten grams of urotropine, one gram oftriisopropanolamine, and two grams of polyvinyl acetate in cc. ofchloroform was applied to a carbon tissue paper loaded with carbonblack. After evaporation of the chloroform, a firmly adhering coatingwith good shelf life was obtained on the support material. Coating wasused for the development of diazotype copies with the action of heat, asdescribed in Example 1.

Example 3 Fifty grams of an ester wax with a melting point of 7882 C.were melted into 20 grams of triethanolamine. The melt was applied bymechanical means to a wax paper base impregnated with carbon black andhaving a coating weight of 30 grams per square meter. The same procedurewas followed as in Example 1. By the action of heat on the coatedmaterial for a short period, the wax coating containing triethanolaminemelted onto the surface of the diazotype material and there, because ofits basic property, it initiated a coupling action in the unexposedareas (image areas) with the formation of a dye.

It is apparent that the described examples are capable of manyvariations and modifications. All such variations and modifications areto be included within the scope of the present invention.

What is claimed is:

1. A method of developing exposed diazotype sheet material comprising:

(a) providing a developer sheet comprising a support,

infrared radiation-absorbing, heat-generating material uniformlydisposed at a surface of said support, and a thermally-activatablealkali-generator uniformly disposed in intimate physical contact withsaid radiation-absorbing material at said support surface;

(b) combining said support surface in intimate contact with thesensitized surface of said diazotype sheet material; and

(c) exposing said radiation-absorbing material to infrared radiation fora time sufficient to generate therein temperatures effective to activatesaid alkali generator.

2. The method according to claim 1 wherein said radiation-absorbingmaterial is carbon black.

3. A method in accordance with claim 1 in which the temperature of thedeveloper sheet is raised to between 50 C. and 200 C. as a result ofinfrared radiation.

4. A method in accordance with claim 1 in which the developer sheet isbetween the source of infrared radiation and the diazotype material.

(References on following page) References Cited by the Examiner3,503,797 1;;192; M11112- 96-49 5 33 233 9M9 312341323 12/1365 213153352; ;i.-:::::: 32:23 12/1956 Marron et 9649 5 NORMAN G. TORCHIN,Primary Examiner.

Z1132? 11112 2525 .jjijijjjjf afi ALEXANDER 11 R1601, 11/1964 Kosar96-49 C. L. BOWERS,JR., AssistantExaminer.

8/1965 Hollmann 9649

1. A METHOD OF DEVELOPING EXPOSED DIAZOTYPE SHEET MATERIAL COMPRISING:(A) PROVIDING A DEVELOPER SHEET COMPRISING A SUPPORT, INFRAREDRADIATION-ABSORBING, HEAT-GENERATING MATERIAL UNIFORMLY DISPOSED AT ASURFACE OF SAID SUPPORT, AND A THERMALLY-ACTIVATABLE ALKALI-GENERATORUNIFORMLY DISPOSED IN INTIMATE PHYSICAL CONTACT WITH SAIDRADIATION-ABSORBING MATERIAL T SAID SUPPORT SURFACE; (B) COMBINING SAIDSUPPORT SURFACE IN INTIMATE CONTACT WITH THE SENSITIZED SURFACE OF SAIDDIAZOTYPE SHEET MATERIAL; AND (C) EXPOSING SAID RADIATION-ABSORBINGMATERIAL TO INFRARED RADIATION FOR A TIME SUFFICIENT TO GENERATE THEREINTEMPEATURES EFFECTIVE TO ACTIVATE SAID ALKALI GENERATOR.